PROJECT SUMMARY Recognition of cell-surface carbohydrates by lectins plays an essential role in biological processes ranging from fertilization and cell signaling to pathogen clearance and immune response. Human intelectins (hIntL-1 and hIntL-2) are a relatively uncharacterized class of lectins that are secreted at mucosal barriers and are implicated in various disease states such as Crohn?s Disease, asthma, and diabetes. Previous work from the Kiessling group has indicated that hIntL-1 specifically recognizes microbial glycans via binding to an exocyclic 1,2-diol motif; however the full binding profiles of hIntL-1 and hIntL-2 have not been investigated. Additionally, the difficulty of capturing intelectin ligands directly from cells makes understanding the correlation between saccharide-binding affinity and cell-binding activity challenging. We hypothesize that the affinities of intelectins for specific chemical epitopes significantly influences their differential cell recognition and are thus associated with their physiological roles. We will test this hypothesis by identifying and characterizing the ligand binding profiles of hIntL-1 and hIntL-2, and by generating new tools for the capture of endogenous intelectin ligands. In Aim 1, I will employ chemical synthesis and biochemical assays to determine and compare binding affinities of hIntL-1 with mono- and oligosaccharide ligands. I will use this data to elucidate structural characteristics that contribute to intelectin binding and specificity, including stereochemistry, substituents, and position within the glycan. In Aim 2, I will design and synthesize bifunctional boronic acids that will act as glycan capture agents through conjugation to hIntL-1 and its endogenous carbohydrate binding partners. These molecules will stabilize the carbohydrate-protein complexes and enable detection and isolation of cellular hIntL-1 ligands. In Aim 3, I will identify and characterize the mucin-binding properties of hIntL-2 through the synthesis of polymeric mucin mimics. By varying the sugar epitopes on the mucin-like polymers, we will be able to glean information about the function of hIntL-2. Together, these studies will deliver key foundational recognition data that will aid in the discovery of the physiological role of intelectins. More broadly, we expect that the ligand-binding information revealed through the proposed work will guide future research into the development of probes and therapies for disease states that are affected by intelectin expression.